The elite U.S. commandos who snatched an alleged plotter of the Benghazi consulate attack were acting on a bare-bones criminal complaint whose crucial details remain secret.

While some operational color and background are coming to light, the legal charges against Ahmed Abu Khatalla are summed up publicly in a one-page document assigning his case to the chief judge of the U.S. District Court in Washington. Even well-placed lawmakers await further details.

“They’ve been pretty close to the chest with the criminal complaint,” acknowledged Rep. Devin Nunes, R-Calif., a member of the House Permanent Select Committee on Intelligence.

The criminal complaint against Abu Khattala was filed last July 15 but it became public only Tuesday following news of his capture. The complaint charges him with killing a person in the course of an attack on a federal facility, providing material support to terrorists and using a firearm in a crime of violence.

The complaint, signed by FBI Special Agent Michael M. Clarke, is accompanied by an affidavit, which remains sealed. The affidavit typically provides details that may include dates, times and places.

“That will be quite telling,” said Rep. Adam Schiff, D-Calif., another member of the House Intelligence panel, adding that “I’d expect a great deal to be made public, and fairly soon.”

For instance, when a criminal complaint was unsealed in 2005 against an alleged Iraqi insurgent named Wesam al Delaema, it came with a five-page detailed affidavit filed by an FBI special agent. Al Delaema was later sentenced to 25 years and returned to the Netherlands.

A team of prosecutors from the U.S. Attorney’s Office in Washington has joined with attorneys with the Justice Department’s National Security Division to press the case. Abu Khattala’s attorney hasn’t yet been publicly identified.

Abu Khattala has spent the past two years as one of Benghazi’s most public figures, the most well-known of the 70 suspected attackers of the U.S. special mission there in September 2012, an assault that killed Chris Stevens, the U.S. ambassador to Libya, along with three other Americans.

Within weeks of the attack, Abu Khattala boasted of his involvement, telling reporters he was there but didn’t lead the assault. He defended Ansar al Shariah, the Islamic extremist group suspected of leading the attack. But publicly there were no details to corroborate his version of events. Libyan officials found it nearly impossible to arrest suspects without facing retaliation from the Islamists who controlled large swaths of the eastern part of the country.

Abu Khattala moved freely through the cities, gave interviews and traveled regularly to the construction sites where he worked.

But while other names came and went since 2012 as potential suspects, Abu Khattala’s never subsided. With that, his reputation as a leading Islamic extremist grew in Libya. But the number of followers behind him was never large, residents in Benghazi said.

In Benghazi, Libya’s second-largest city, which often feels like a small town, there was surprise among residents that they’d learned about Abu Khattala’s arrest from the United States rather than from other Libyans. At first, many didn’t believe it, but by Wednesday residents sought to piece together how he’d disappeared so furtively.

According to Libyans there, along with U.S. officials, Abu Khattala was picked up on the southwestern desert road that connects Benghazi with the city of Ajdabiya when a group of cars surrounded him as he traveled alone. He didn’t resist, officials said, and was soon taken to a ship.

The Libya Herald, an English-language newspaper based in Tripoli, reported Wednesday that Abu Khattala was en route to meeting a member of the Muslim Brotherhood for dinner when he was seized.

Justice Minister Salah Marghani ordered U.S. officials to return Abu Khattala even as Libyan forces proved incapable of capturing him and its justice system too nascent to try him.

Abu Khattala is on a U.S. Navy ship en route to the United States, where he’s reportedly undergoing interrogation. The Associated Press reported that he’s on the USS New York, an amphibious transport ship constructed in part with steel taken from the destroyed World Trade Center. His arrival date and the next steps, including his first appearance in a U.S. courthouse, aren’t yet known.

“There’s not much that’s common about this case,” said Schiff, himself a former federal prosecutor.

Schiff praised as the “right decision” the Obama administration’s election to try Abu Khattala in conventional civilian court rather than in a military commission operating out of Guantanamo Bay, as some conservative lawmakers have urged.

“Abiding by due process also means promptly bringing Abu Khattala before a judge and allowing him a lawyer before questioning,” added Laura Pitter, acting senior national security counsel at Human Rights Watch.